Illumination apparatus including semiconductor light emitting diodes

ABSTRACT

An illumination apparatus of a high efficiency light emitting element and a driving circuit of a light emitting element controlling a series and parallel connection relationship between light emitting groups according to a voltage level of a driving voltage and controlling a sequential driving of the light emitting groups at the same time.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/344,810, filed on Mar. 13, 2014, which is the National Stage Entry ofInternational Application PCT/KR2012/007409, filed on Sep. 17, 2012, andclaims priority from and the benefit of Korean Patent Application No.10-2011-0093362, filed on Sep. 16, 2011 and Korean Patent ApplicationNo. 10-2012-0056307, filed on May 25, 2012, which are incorporatedherein by reference for all purposes as if fully set forth herein.

BACKGROUND

1. Field

Example embodiments of the present invention relate in general to thefield of an illumination apparatus using semiconductor light emittingdiodes (LEDs) as a light source, and more specifically to anillumination apparatus using semiconductor LEDs that can enable all LEDsto emit light in consideration of fluctuations in the magnitude of analternating current (AC) voltage when a plurality of LEDs are drivenusing the AC voltage.

2. Discussion of the Background

In recent years, a semiconductor light emitting diode (LED) has beenutilized as a light source in many fields due to its variouscharacteristics, such as high efficiency, low power, and high luminance.In particular, the use of illumination systems adopting semiconductorLEDs instead of conventional incandescent light bulbs or fluorescentlamps in the field of illumination has rapidly increased in recenttimes.

Since conventional illumination apparatuses using incandescent lightbulbs or fluorescent lamps as light sources emit light usingcommercially available alternating current (AC) voltage, semiconductorLEDs for illumination also should be capable of being driven using an ACvoltage.

Typically, to drive semiconductor LEDs using an AC voltage, a circuitmay be configured to convert an AC voltage having positive and negativevalues into a rectifying current voltage having a positive value, and toadjust the number of emitting semiconductor LEDs with fluctuations inthe magnitude of the rectifying current voltage.

In the above-described typical technique, with fluctuations in themagnitude of the rectifying current voltage, some of the plurality ofsemiconductor LEDs may continuously emit light over an extended lightemitting time, while some of the remaining semiconductor LEDs emit lightonly when the magnitude of the rectifying current voltage is equal to orhigher than a specific value. Thus, semiconductor LEDs constituting anillumination apparatus may have different light emitting times. As aresult, some of the semiconductor LEDs constituting the illuminationapparatus may wear out earlier than the others, thereby deteriorating alight emitting state of the illumination apparatus and even preventingoperation of the illumination apparatus.

SUMMARY OF THE INVENTION

Accordingly, example embodiments of the present invention are providedto substantially obviate one or more problems due to limitations anddisadvantages of the related art.

Example embodiments of the present invention provide an illuminationapparatus using semiconductor light emitting diodes (LEDs) that canenable all the LEDs to emit light in consideration of fluctuations inthe magnitude of an alternating current (AC) voltage for driving theLEDs.

In some example embodiments, an illumination apparatus includes arectifier configured to receive AC power and generate a driving voltagein the form of a rectifying current voltage, a control signal generatorconfigured to compare the driving voltage with a predetermined referencevoltage to generate a sampling signal, and configured to perform a logicoperation on the sampling signal to generate a switch control signal anda current control signal, a switch unit configured to perform on/offoperations in response to the switch control signal and selectivelytransmit the driving voltage, a total current controller configured toreceive the sampling signal and generate a target voltage as an analogsignal, a current controller configured to be enabled in response to thecurrent control signal and having a plurality of driving currentcontrollers configured to receive the target voltage and determine adriving current, and a light emitting unit connected to the currentcontroller and having light emitting diodes (LEDs) configured to performa light emitting operation.

According to an example embodiment of the present invention, there isprovided an illumination apparatus including: a rectifier configured tobe connected to alternating current (AC) power to perform a full-waverectification for an applied AC voltage, and to provide a rectifiedvoltage which is full-wave rectified to a light emitting unit as adriving voltage; the light emitting unit configured to include a firstlight emitting group to an n-th light emitting group (n is a positiveinteger of two or more) and to emit light by receiving the drivingvoltage from the rectifier; a control signal generator configured togenerate a switch control signal for controlling a series and parallelconnection relationship between the first light emitting group to then-th light emitting group according to an average voltage level perperiod of the driving voltage, and generate a current control signal forcontrolling a sequential driving of at least some of the first lightemitting group to the n-th light emitting group according to the voltagelevel of the driving voltage; a switch unit configured to perform an onor off operation according to the switch control signal to selectivelytransfer the driving voltage; and a current controller configured to beconnected to the first light emitting group to the n-th light emittinggroup, respectively, and have a first driving current controller to ann-th driving current controller which are selectively activatedaccording to the current control signal.

The control signal generator may be configured to control magnitude of adriving current of the light emitting element according to the averagevoltage level per period of the driving voltage.

According to another example embodiment of the present invention, thereis provided a driving circuit of a light emitting element controlling adriving of a light emitting unit including a first light emitting groupto an n-th light emitting group (n is a positive integer of two or more)including: a rectifier configured to be connected to alternating current(AC) power to perform a full-wave rectification for an applied ACvoltage, and to provide a rectified voltage which is full-wave rectifiedto a light emitting unit as a driving voltage; a control signalgenerator configured to generate a switch control signal for controllinga series and parallel connection relationship between the first lightemitting group to the n-th light emitting group according to an averagevoltage level per period of the driving voltage, and generate a currentcontrol signal for controlling a sequential driving of at least some ofthe first light emitting group to the n-th light emitting groupaccording to the voltage level of the driving voltage; a switch unitconfigured to perform an on or off operation according to the switchcontrol signal to selectively transfer the driving voltage; and acurrent controller configured to be connected to the first lightemitting group to the n-th light emitting group, respectively, and havea first driving current controller to an n-th driving current controllerwhich are selectively activated according to the current control signal.

The control signal generator may be configured to control magnitude of adriving current of the light emitting element according to the averagevoltage level per period of the driving voltage.

According to the present invention, an electrical connectionrelationship among the plurality of LEDs can be appropriately changedwith fluctuations in the magnitude of an AC voltage for driving theplurality of LEDs, so that all of the plurality of LEDs employed in theillumination apparatus can emit light.

According to the present invention, all of the plurality of LEDs canemit light, thereby preventing some of the LEDs employed in theillumination apparatus from emitting light for a longer time anddeteriorating earlier than the other LEDs.

Furthermore, according to the present invention, when necessary, thetotal current supplied to all the LEDs can be controlled to be constantor current supplied to each of the LEDs can be controlled to beconstant.

While the example embodiments of the present invention and theiradvantages have been described in detail, it should be understood thatvarious changes, substitutions and alterations may be made hereinwithout departing from the scope of the invention.

BRIEF DESCRIPTION OF DRAWINGS

Example embodiments of the present invention will become more apparentby describing in detail example embodiments of the present inventionwith reference to the accompanying drawings, in which:

FIG. 1 is a circuit diagram of an illumination apparatus using asemiconductor light emitting diode (LED) according to a first exampleembodiment of the present invention;

FIG. 2 is a circuit diagram of a control signal generator of FIG. 1;

FIG. 3 is a circuit diagram of respective components of a currentcontroller of FIG. 1;

FIG. 4 is a block diagram of a total current controller of FIG. 1;

FIG. 5 is a graph for explaining operations of the illuminationapparatus of FIG. 1, according to the first example embodiment of thepresent invention;

FIG. 6 is another graph for explaining operations of the illuminationapparatus of FIG. 1, according to the first example embodiment of thepresent invention;

FIG. 7 is a circuit diagram of an illumination apparatus using asemiconductor LED according to a second example embodiment of thepresent invention;

FIG. 8 is a circuit diagram of a control signal generator according tothe second example embodiment of the present invention;

FIG. 9 is a circuit diagram of a switching unit according to the secondexample embodiment of the present invention.

FIG. 10 is a circuit diagram of an illumination apparatus using asemiconductor light emitting element according to a third exampleembodiment of the present invention;

FIG. 11A is a waveform diagram showing a relationship between a drivingvoltage and a driving current of the light emitting element in a case inwhich the illumination apparatus using the semiconductor light emittingelement according to the third example embodiment of the presentinvention is connected to AC power of 120V(rms); and

FIG. 11B is a waveform diagram showing the relationship between thedriving voltage and the driving current of the light emitting element ina case in which the illumination apparatus using the semiconductor lightemitting element according to the third example embodiment of thepresent invention is connected to AC power of 220V(rms).

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Example embodiments of the present invention are disclosed herein.However, specific structural and functional details disclosed herein aremerely representative for purposes of describing example embodiments ofthe present invention, however, example embodiments of the presentinvention may be embodied in many alternate forms and should not beconstrued as limited to example embodiments of the present invention setforth herein.

Accordingly, while the invention is susceptible to various modificationsand alternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Itshould be understood, however, that there is no intent to limit theinvention to the particular forms disclosed, but on the contrary, theinvention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention. Like numbers referto like elements throughout the description of the figures.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present invention. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(i.e., “between” versus “directly between”, “adjacent” versus “directlyadjacent”, etc.).

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”,“comprising,”, “includes” and/or “including”, when used herein, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

It should also be noted that in some alternative implementations, thefunctions/acts noted in the blocks may occur out of the order noted inthe flowcharts. For example, two blocks shown in succession may in factbe executed substantially concurrently or the blocks may sometimes beexecuted in the reverse order, depending upon the functionality/actsinvolved.

According to an example embodiment of the present invention, a term“light emitting group” refers to a collection of light emitting elementsin which a plurality of light emitting elements (or a plurality of lightemitting cells) are connected in series with/in parallel to/in serieswith and in parallel to each other, so that an operation thereof iscontrolled (i.e., simultaneously turned on/off) as a single unitaccording to a control of a control signal generator and a currentcontroller.

In addition, a term ‘first forward voltage level VF1’ refers to athreshold voltage level capable of driving a first light emitting group,a term ‘second forward voltage level VF2’ refers to a threshold voltagelevel capable of driving the first light emitting group and a secondlight emitting group which are connected in series with each other(i.e., a voltage level obtained by summing the forward voltage level ofthe first light emitting group and the forward voltage level of thesecond light emitting group), and a term ‘third forward voltage levelVF3’ refers to a threshold voltage level capable of driving first tothird light emitting groups which are connected in series with eachother. That is, an ‘n-th forward voltage level VFn’ refers to athreshold voltage level capable of driving first to n-th light emittinggroups which are connected in series with each other (i.e., the voltagelevel obtained by summing all of the forward voltage level of the firstlight emitting group to the forward voltage level of the n-th lightemitting group). Hereinafter, although the present invention will bedescribed based on example embodiments in which all of the lightemitting groups have the same forward voltage level, it will be apparentto those skilled in the art that the forward voltage levels of therespective light emitting groups may be designed to be different fromeach other, if necessary. Therefore, hereinafter, example embodiments ofthe present invention will be described based on an example embodimentin which the first forward voltage level is 1VF, the second forwardvoltage level is 2VF, and similarly, the n-th forward voltage level isnVF.

In addition, in the present specification, a ‘first operation section’refers to a section in which the driving voltage provided to the lightemitting unit is the first forward voltage level VF1 or more and is lessthan the second forward voltage level VF2, a ‘second operation section’refers to a section in which the driving voltage provided to the lightemitting unit is the second forward voltage level VF2 or more and isless than the third forward voltage level VF3, and similarly, an ‘n-thoperation section’ refers to a section in which the driving voltageprovided to the light emitting unit is the n-th forward voltage levelVFn or more.

In addition, in the present specification, a ‘sequential driving’ refersto a driving method in which the first light emitting group to the n-thlight emitting group are sequentially tuned on and are sequentiallyturned off depending on a voltage level of a driving voltage Vin.

In addition, terms such as V1, V2, V3, . . . , t1, t2, . . . , T1, T2,T3, and the like used for expressing any certain voltages, certaintimings, certain temperatures, and the like in the present specificationare not used to express absolute values, but are relative values used tobe distinguishable from each other.

Various example embodiments will now be described more fully withreference to the accompanying drawings in which some example embodimentsare shown. The present invention may, however, be embodied in differentforms and should not be construed as limited to the embodiments setforth herein. Rather, these embodiments are provided so that thisdisclosure is thorough and complete and fully conveys the scope of thepresent invention to one skilled in the art. Also, since terms aredefined in consideration of functions of the present invention, they mayvary according to users' intentions or practice. Hence, the terms shouldnot be interpreted as limiting technical components of the presentinvention.

Embodiment 1

FIG. 1 is a circuit diagram of an illumination apparatus using asemiconductor LED according to a first example embodiment of the presentinvention.

FIG. 1 illustrates an example of the illumination apparatus that adoptsfour LEDs L1 to L4. However, the present invention is not limited by thenumber of LEDs, and it would be apparent to those skilled in the artthat the illumination apparatus of FIG. 1 may be modified into anillumination apparatus according to another example embodiment that usesat least two LEDs connected in series or an LED including a plurality oflight emitting chips connected in series or parallel.

As shown in FIG. 1, an illumination apparatus using a semiconductor LEDaccording to an example embodiment of the present invention may includea rectifier 100, a control signal generator 110, a switching unit 120, acurrent controller 130, a total current controller 140, and a lightemitting unit 150.

The rectifier 100 may rectify an AC voltage VAC having positive andnegative values and convert the rectified AC voltage into a drivingvoltage Vin in the form of a rectifying current voltage. One of variousknown rectifier circuits, such as a diode bridge circuit includingdiodes, may be adopted as the rectifier 100.

The control signal generator 110 may receive the driving voltage Vin,generate switch control signals SW1 to SW3 for controlling on/offoperations of the switch unit 120, generate current control signals SC1to SC4 for controlling operations of the current controller 130, andgenerate sampling signals COM0 to COM3 for determining a target voltageVt, which is an output of the total current controller 140.

The switch unit 120 may include a plurality of switches 121, 122, and123 connected in parallel to one another, and perform on/off operationsin response to the switch control signals SW1 to SW3. Thus, the drivingvoltage Vin may be selectively applied to the LEDs L2 to L4.

The current controller 130 may be connected to a cathode terminal ofeach of the LEDs L1 to L4 and control operations of the connected LEDsin response to the current control signals SC1 to SC4. Also, the targetvoltage Vt may be applied to the current controller 130. Current amountsof the LEDs L1 to L4 connected to the current controller 130 may bedetermined according to the applied target voltage Vt.

To this end, the current controller 130 may include a plurality ofdriving current controllers 131, 132, 133, and 134. The driving currentcontrollers 131, 132, 133, and 134 may be connected in parallel to oneanother.

For example, the first driving current controller 131 may receive acurrent control signal SC1 and a target voltage Vt. The first drivingcurrent controller 131 may be enabled or disabled in response to thecurrent control signal SC1. When enabled, the first driving currentcontroller 131 may allow a driving current corresponding to the targetvoltage Vt to flow through the LED L1.

The total current controller 140 may receive sampling signals COM0 toCOM3 of the control signal generator 110 and convert the samplingsignals COM0 to COM3 into analog signals. The converted analog signalsmay be applied in the form of the target voltage Vt to the currentcontroller 130.

The light emitting unit 150 may include a plurality of LEDs L1 to L4 anda plurality of diodes D1 to D3. For example, the LED L1 may be connectedbetween the driving voltage Vin and the first driving current controller131. Also, the remaining LEDs L2 to L4 may be connected between theswitch unit 120 and the driving current controllers 132, 133, and 134.For instance, the LED L1 may be expressed as a first light emittinggroup, and the remaining LEDs L2 to L4 may be expressed as a secondlight emitting group. The first light emitting group may be directlyconnected to the driving voltage Vin and perform a light emittingoperation. Conversely, the second light emitting group may receive thedriving voltage Vin only when each of the switches 121, 122, and 123 ofthe switch unit 120 is in a conduction state.

FIG. 2 is a circuit diagram of the control signal generator of FIG. 1.

Referring to FIG. 2, the control signal generator may include acomparison unit 112 and a logic combination unit 114.

The comparison unit 112 may receive the driving voltage Vin output fromthe rectifier 100 and compare the driving voltage Vin with a referencevoltage VF. A comparison result may be indicated by levels of thesampling signals COM0 to COM3. To this end, the comparison unit 112 mayinclude a plurality of voltage division resistors Rs1 to Rs5 connectedin series between the driving voltage Vin and ground. Also, branchesfrom nodes between the voltage division resistors Rs1 to Rs5 may beapplied to the comparators 1121 to 1124. Voltages of the nodes betweenthe voltage division resistors Rs1 to Rs5 may be applied to positiveinput terminals of the comparators 1121 to 1124, and the referencevoltage VF may be applied in common to negative input terminals of thecomparators 1121 to 1124.

When the voltages of the nodes between the voltage division resistorsRs1 to Rs5 applied to the positive input terminals of the respectivecomparators 1121 to 1124 are higher than the reference voltage VFapplied to the negative input terminals thereof, the comparators 1121 to1124 may output high-level signals. Also, when the voltages of the nodesbetween the voltage division resistors Rs1 to Rs5 applied to thepositive input terminals of the respective comparators 1121 to 1124 arelower than the reference voltage VF applied to the negative inputterminals thereof, the comparators 1121 to 1124 may output low-levelsignals.

The logic combination unit 114 may include a first logic unit 115 and asecond logic unit 116.

The first logic unit 115 may receive the sampling signals COM0 to COM3output by the respective comparators 1121 to 1124, perform logiccombination operations on the sampling signals COM0 to COM3, andgenerate current control signals SC1 to SC4. The current control signalsSC1 to SC4 may control operations of the current controller 130 ofFIG. 1. The first logic unit 115 may include a combination of variouslogic devices according to signals of inputs and outputs. Also, aselection signal SEL may be applied to the first logic unit 115. Theselection signal SEL may select a sampling signal on which a logicoperation will be performed.

The second logic unit 116 may receive the sampling signals COM0 to COM3,perform logic combination operations on the sampling signals COM0 toCOM3, and generate switch control signals SW1 to SW3. Each of the switchcontrol signals SW1 to SW3 may control the switch unit 120 of FIG. 1.The second logic unit 116 may include a combination of various logicdevices according to signals of inputs and outputs. Also, the selectionsignal SEL may be applied to the second logic unit 116. The selectionsignal SEL may select a predetermined sampling signal on which a logicoperation will be performed.

Each of the first logic unit 115 and the second logic unit 116 mayinclude a combination of logic devices, which may be variously selectedaccording to phases of the input sampling signals COM0 to COM3 andphases of the switch control signals SW1 to SW3 or current controlsignals SC1 to SC4. For example, each of the two logic units 115 and 116may include a programmable logic array or programmable array logic.

Also, the number of sampling signals may not be specifically limited butmay be variously selected according to the number of output switchcontrol signals and the number of current control signals.

FIG. 3 is a circuit diagram of respective components of the currentcontroller of FIG. 1.

The circuit diagram of FIG. 3 illustrates any one of four drivingcurrent controllers constituting the current controller.

Referring to FIG. 3, the driving current controller may include a linearamplifier 1301, a buffer 1302, a driving transistor Qd, and a detectionresistor Rd.

A voltage detected by the detection resistor Rd may be applied to anegative input terminal of the linear amplifier 1301. Also, the targetvoltage Vt may be applied to a positive input terminal of the linearamplifier 1301. The target voltage Vt may be a voltage generated by thetotal current controller 140 of FIG. 1. An output of the linearamplifier 1301 may be applied to the buffer 1302. The buffer 1302 may beenabled or disabled in response to the current control signals SC0 toSC3.

The term “enabling” refers to performing, by a target element, aninput/output (I/O) function. Also, the term “disabling” refers toentering, by a target element, an off state or floated state withoutperforming functions. Accordingly, during a disabling mode, theprocessing or transmission of signals may not occur. Hereinafter, themeanings of enabling and disabling in the present invention should beinterpreted as described above.

The enabled buffer 1302 may transmit the output of the linear amplifier1301 to the drive transistor Qd. The drive transistor Qd may beconnected between the cathode terminal of each of the LEDs L1 to L4 andthe detection resistor Rd. Also, the drive transistor Qd may performon/off operations in response to the output of the buffer 1302 appliedto a gate terminal thereof. The buffer 1302 may be any device configuredto be capable of on/off operations in response to the current controlsignal SC. Accordingly, the buffer 1302 may be replaced by a switch.

When the buffer 1302 is enabled, a negative feedback including the drivetransistor Qd, the linear amplifier 1301, and the buffer 1302 may beformed. When a detection voltage of the detection resistor Rd is lowerthan the target voltage Vt, the linear amplifier 1301 may output ahigh-level signal, which may be applied through the buffer 1302 to thegate terminal of the drive transistor Qd. A gate-source voltage Vgs ofthe drive transistor Qd may increase due to the increased voltage level.Thus, the amount of current flowing through the detection resistor Rdmay increase. A detection voltage of the detection resistor Rd mayincrease due to the increased amount of current. That is, the detectionvoltage of the detection resistor Rd may be characterized by followingthe target voltage Vt.

When the buffer 1302 is disabled, the buffer 1302 may output a low-levelsignal or enter a floated state so that the drive transistor Qd mayenter an off state.

As a result, no current may be supplied to the driving currentcontroller.

FIG. 4 is a block diagram of the total current controller 140 of FIG. 1.

Referring to FIG. 4, the total current controller 140 may include adigital-to-analog converter (DAC) 141 configured to receive the samplingsignals COM0 to COM3 generated by the control signal generator 110 shownin FIG. 2 and output a predetermined target value according to a stateof each of the sampling signals COM0 to COM3. For example, the DAC 141may receive logic values 0000 to 1111 of the sampling signals COM0 toCOM3 and output a voltage corresponding to the predetermined targetvalue in response to each of the logic values 0000 to 1111. The targetvoltage Vt corresponding to the target value may be input through thebuffer 143 to the linear amplifier 1301 of each of the driving currentcontrollers 131, 132, 133, and 134.

In addition, although FIG. 4 illustrates that the total currentcontroller 140 outputs only one output, this is only an example. Thus,the total current controller 140 may output a plurality of outputscorresponding to the number of driving current controllers to which thetarget voltages Vt are applied. Also, a plurality of output targetvoltages Vt may have different values.

Also, the selection signal SEL may be input to the total currentcontroller 140. When the selection signal SEL is enabled, the totalcurrent controller 140 may output different target voltages Vt.

FIG. 5 is a graph illustrating operations of the illumination apparatusof FIG. 1, according to the first example embodiment of the presentinvention.

Referring to FIG. 5, a driving voltage Vin, a magnitude of the totalcurrent IT flowing through all the LEDs, and a magnitude of current ILflowing through each of the LEDs are shown.

One cycle of the driving voltage Vin in the form of a rectifying currentvoltage is shown. Here, the driving voltage Vin periodically increasesand decreases between 0V and a peak voltage. As shown in FIG. 5, the sumof currents flowing through all the LEDs L1 to L4, that is, themagnitude of the total current IT, may be controlled to be constant.

The switch unit 120 and the current controller 130 may be controlled asshown in Table 1.

TABLE 1 First Second Third Fourth driving driving driving drivingcurrent current current current First Second Third controller controllercontroller controller switch switch switch 131 132 133 134 121 122 123VF ≦ Vin < 2VF ON ON ON ON ON ON ON 2VF ≦ Vin < 3VF OFF ON OFF ON OFF ONOFF 3VF ≦ Vin < 4VF OFF OFF ON OFF OFF OFF OFF OFF OFF ON ON ON OFF OFF4VF ≦ Vin OFF OFF OFF ON OFF OFF OFF

Operations shown in Table 1 according to the first embodiment will bedescribed with reference to FIGS. 1 through 3.

For brevity, it is assumed in FIG. 2 that the resistor Rs5 is removed orhas an immaterial value. Accordingly, it is assumed that the drivingvoltage Vin is applied to the comparator 1124 without causing a drop inthe level of the driving voltage Vin.

When the driving voltage Vin output by the rectifier 100 graduallyincreases from 0 V to a value equal to or higher than the referencevoltage VF and lower than 2VF, the sampling signal COM3 output by thecomparator 1124 may become a high-level signal. Sampling signals outputby the remaining comparators 1121, 1122, and 1123 may become low-levelsignals. The reference voltage VF may be a forward voltage by which eachLED L1 or L4 may initiate a light emitting operation.

The first logic unit 115 receiving the output of the comparison unit 112may enable all the current control signals SC1 to SC4. Also, the secondlogic unit 116 may enable all the switch control signals SW1 to SW3.Thus, all the switches 121, 122, and 123 of the switch unit 120 may beturned on, while all the driving current controllers 131, 132, 133, and134 may be enabled.

That is, in FIG. 2, the sampling signals COM0 to COM3 may be input inthe form of (0001) to the first logic unit 115 and the second logic unit116. The first logic unit 115 receiving the sampling signals COM0 toCOM3 d may enable all the current control signals SC1 to SC4. Forexample, all the current control signals SC1 to SC4 may be enabled to ahigh level. Also, the second logic unit 116 may enable the switchcontrol signals SW1 to SW3. Accordingly, the first through thirdswitches 121 to 123 may be turned on. All the LEDs L1 to L4 may beconnected in parallel by the turned-on switches 121, 122, and 123 andthe enabled driving current controllers 131, 132, 133, and 134.

In addition, the DAC 141 of the total current controller 140 may receivea logic signal (e.g., 0001) of the sampling signals COM0 to COM3 outputby the comparison unit 112 of the control signal generator 110 andgenerate the target voltage Vt corresponding to the predetermined targetvalue in response to the logic signal. In this case, the target valuemay be a value equal to ¼ the total current IT so as to constantlycontrol the total current IT.

Due to the above-described operation, all the driving currentcontrollers 131, 132, 133, and 134 and the switches 121, 122, and 123may be put into a conduction state or enabled, and the plurality of LEDsL1 to L4 may be electrically connected in parallel to one another due tostates of the driving current controllers 131, 132, 133, and 134 and theswitches 121, 122, and 123. As a result, the total driving current ITmay be divided by four and supplied to the respective LEDs L1 to L4.

To sum up, when the driving voltage Vin is equal to or higher than thereference voltage VF, high-level current control signals SC1 to SC4 maybe applied from the control signal generator 110 to the buffers 1302 ofthe respective driving current controllers 131, 132, 133, and 134, andthe target voltage Vt corresponding to a target value equal to ¼ thetotal driving current IT may be applied from the total currentcontroller 140 to the linear amplifiers 1301 of the respective drivingcurrent controllers 131, 132, 133, and 134. Thus, the linear amplifier1301 may adjust a gate voltage of the driving transistor Qd such that avoltage applied to the detection resistor Rd is equal to the targetvoltage Vt so that current corresponding to ¼ the total driving currentIT may flow between source and drain terminals of the driving transistorQd. As a result, current IL corresponding to ¼ the total driving currentIT may be divided and supplied to each of the LEDs L1 to L4.

When the magnitude of the driving voltage Vin output by the rectifier100 gradually increases to a value higher than or equal to 2VF, andlower than 3VF, the control signal generator 110 may generate and outputa switch control signal by which two of the LEDs L1 to L4 may beconnected in series. That is, the two comparators 1123 and 1124 of FIG.2 may output high-level signals.

The sampling signals COM0 to COM3 output by the comparators 1121 to 1124may be output in the form of (0011).

In addition, the first logic unit 115 receiving the sampling signalsCOM0 to COM3 may enable the current control signals SC2 to SC4.

Accordingly, current flowing through the LED L2 may be supplied to thesecond driving current controller 132, and current supplied to the LEDL4 may be supplied to the fourth driving current controller 134.

In addition, the second logic unit 116 receiving the sampling signalsCOM0 to COM3 may enable the switch control signal SW2. Accordingly, thesecond switch 122 may be turned on, while the remaining switches 121 and123 may be turned off.

The total current controller 140 may receive the sampling signals COM0to COM3 in the form of (0011). The input sampling signals COM0 to COM3may be converted into analog signals and output as a target voltage Vt.The target voltage Vt may allow the driving current IL of the enableddriving current controllers 142 and 144 to be ½ the total current IT.

Due to the operations of the switch unit 120 and the current controller130, the second switch 122 may be turned on, and the second drivingcurrent controller 142 and the fourth driving current controller 144 maybe enabled. Thus, a current path including the LED L1, the diode D1, theLED L2, and the second driving current controller 142 may be formed, andanother current path including the LED L3, the diode D3, the LED L4, andthe fourth driving current controller 144 may be formed.

As a result, the total driving current IT may be halved and supplied tothe respective current paths.

When the driving voltage Vin output by the rectifier 100 is higher thanor equal to 3VF, and lower than 4VF, the control signal generator 110may generate switch control signals SW1 to SW3 by which three of theLEDs L1 to L4 may be connected in series, and output current controlsignals SC1 to SC4.

The sampling signals COM0 to COM3 output by the comparison unit 112 ofthe control signal generator 110 may be output in the form of (0111).This means that the sampling signal COM0 is a low-level signal, and theremaining sampling signals COM1 to COM3 are high-level signals.

The first logic unit 115 receiving the sampling signals COM0 to COM3 mayenable the current control signal SC3. Thus, only the third drivingcurrent controller 133 may be enabled and the remaining driving currentcontrollers 131, 132, and 134 disabled.

Also, the second logic unit 116 receiving the sampling signals COM0 toCOM3 may disable all the switch control signals SW1 to SW3. Accordingly,all the switches 121, 122, and 123 of the switch unit 120 may be turnedoff.

Thus, a current path including the LED L1, the diode D1, the LED L2, thediode D2, the LED D3, and the third driving current controller 133 maybe formed. Accordingly, three LEDs L1, L2, and L3 of FIG. 1 may performlight emitting operations.

Furthermore, the total current controller 140 may receive the samplingsignals COM0 to COM3 and convert the sampling signals COM0 to COM3 intothe target voltages Vt. That is, the total current controller 140 mayreceive the logic signal (0111) and generate the target voltage Vt inresponse to the logic signal (0111). Since only the three LEDs L1, L2,and L3 connected in series are operated in response to the generatedtarget voltage Vt, a level of the generated target voltage Vt may have avalue corresponding to the total current.

In addition, the LED L4, which is not connected in series to the LEDsL1, L2, and L3, may selectively emit light. To this end, an externallyinput selection signal SEL may be applied to the first and second logicunits 115 and 116 of the control signal generator 110. When theselection signal SEL is enabled, the first logic unit 115 may enable thecurrent control signals SC3 and SC4. Thus, the third driving currentcontroller 133 and the fourth driving current controller 134 may beenabled. Also, the second logic unit 116 may receive the enabledselection signal SEL, perform a logic operation on the enabled selectionsignal SE, and enable the switch control signal SW1. Accordingly, thefirst switch 121 may be turned on.

Thus, a current path including the LED L1, the diode D1, the LED L2, thediode D2, the LED L3, and the third driving current controller 133 maybe formed, and another current path including the LED L4 and the fourthdriving current controller 134 may be formed.

In addition, the selection signal SEL may be applied to the totalcurrent controller 140. The DAC 141 constituting the total controller140 may receive the selection signal SEL in addition to the samplingsignals COM0 to COM3 of the control signal generator 110. When theselection signal SEL is enabled, the total current controller 140 maygenerate two kinds of target voltages. For instance, the total currentcontroller 140 may process the sampling signals COM0 to COM3 to generatea target voltage Vt1 applied to the third driving current controller133, and generate a target voltage Vt2 applied to the fourth drivingcurrent controller 134 sing the sampling signals COM0 to COM3 and theselection signal SEL.

The target voltage Vt1 applied to the third driving current controller133 may be set as a value corresponding to ¾ the total driving currentIT, and the target voltage Vt2 applied to the fourth driving currentcontroller 134 may be set as a value corresponding to ¼ the totaldriving current IT.

When the driving voltage Vin, which is an output voltage of therectifier 100, is at least 4 times the reference voltage VF, all thecomparators 1121 to 1124 of the control signal generator 110 maygenerate high-level signals. Accordingly, the sampling signals COM0 toCOM3 may have a logic value (1111).

The first logic unit 115 receiving the sampling signals COM0 to COM3 mayenable the current control signal SC4.

Thus, the fourth driving current controller 134 may be enabled. Also,the second logic unit 116 receiving the sampling signals COM0 to COM3may disable all switch control signals. Accordingly, all the switches121, 122, and 123 of the switch unit 120 may be turned off.

Accordingly, in FIG. 1, a current path including the LED L1, the diodeD1, the LED L2, the diode D2, the LED L3, the diode D3, the LED L4, andthe fourth driving current controller 134 may be formed.

Also, the total current controller 140 may receive the sampling signalsCOM0 to COM3 output by the comparison unit 112 of the control signalgenerator 110 and convert the sampling signals COM0 to COM3 into atarget voltage Vt, which is an analog signal. The target voltage Vt maybe applied to the fourth driving current controller 134, which may drivecurrent corresponding to the total current driving current IT.

Referring to FIG. 5, the magnitude of the total current IT may becontrolled to be constant in the form of one square wave. Even if thedriving voltage Vin varies, the total current IT may be appropriatelydivided and supplied to respective LEDs. Current flowing through each ofthe LEDs may vary according to a level of the driving voltage Vin. Inthe above-described case, the average amounts of power supplied to therespective LEDs may be equalized, and a power factor and criticalconditions may be satisfied.

FIG. 6 is another graph illustrating operations of the illuminationapparatus of FIG. 1, according to the first example embodiment of thepresent invention.

Referring to FIG. 6, a driving voltage Vin, a magnitude of the totalcurrent IT flowing through all the LEDs, and a magnitude of current ILflowing through each of the LEDs are shown.

Although the operations described with reference to FIG. 5 arecharacterized by constantly controlling the magnitude of the totalcurrent IT, in FIG. 6, even if switching conditions are changed, themagnitude of current IL flowing through each of the LEDs is controlledto be constant to maintain a constant light emitting amount.

Since the switching conditions are the same as in Table 1, a descriptionthereof will be omitted. Also, an equal amount of current flows througheach of the LEDs, a process of generating the target voltage Vt usingsampling signals may be omitted. Accordingly, in addition to generationof the target voltage Vt using the total current controller 140, thetarget voltage Vt may be applied to the respective driving currentcontrollers 131, 132, 133, and 134 using an additional supply voltage.

To begin with, when the driving voltage Vin output by the rectifier 100gradually increases from 0V to a value equal to or higher than thereference voltage VF and lower than 2VF, the four LEDs L1 to L4 may beconnected in parallel to one another.

In this case, the total current controller 140 may supply the targetvoltage Vt such that a predetermined reference current Iref is suppliedto each of the driving current controllers 131, 132, 133, and 134. Thus,the reference current Iref may flow through each of the LEDs, and thetotal current amount may become 4Iref.

Subsequently, when the driving voltage Vin output by the rectifier 100reaches a value equal to or higher than 2VF and lower than 3VF, an arrayincluding two LEDs L1 and L2 connected in series and an array includingtwo LEDs L3 and L4 connected in series may be connected in parallel toeach other. In this case, the total current controller 140 may supplythe target voltage Vt to the second driving current controller 132 andthe fourth driving current controller 134. Thus, the reference currentIref may flow through the LEDs L1 and L2 connected in series and alsoflow through the LEDs L3 and L4 connected in series. Accordingly, thetotal current amount may become 2Iref.

Thereafter, when the driving voltage Vin output by the rectifier 100reaches a value equal to or higher than 3VF, and lower than 4VF, anarray including three LEDs L1 to L3 connected in series may be connectedin parallel to one LED L4. The total current controller 140 may supplythe target voltage Vt to the third driving current controller 133 andthe fourth driving current controller 134. Each of the driving currentcontrollers 133 and 134 may drive the reference current Iref.Accordingly, the total current amount may become 2Iref.

Thereafter, when the magnitude of the driving voltage Vin output by therectifier 100 is 4VF or higher, all the LEDs L1 to L4 may be connectedin series. The total current controller 140 may supply the targetvoltage Vt to the fourth driving current controller 134. According, thetotal current amount may become Iref.

As shown in FIG. 6, the total current IT may vary according to themagnitude of the driving voltage Vin. Also, current flowing through oneLED may be always controlled to be constant. In this case, the averageamounts of power supplied to the respective LEDs may differ from oneanother. However, even if a connection relationship among the respectiveLEDs is changed, since light emitting amounts of the respective LEDs arealways maintained constant, the illumination apparatus can maintainconstant brightness.

Embodiment 2

FIG. 7 is a circuit diagram of an illumination apparatus using asemiconductor LED according to a second example embodiment of thepresent invention.

FIG. 7 illustrates an example of the illumination apparatus that adoptsfour LEDs. However, the present invention is not limited by the numberof LEDs, and each of the LEDs may be one LED obtained by modeling aserial connection structure of at least two LEDs, a parallel connectionstructure of at least two LEDs, or a mixture of serial and parallelconnection structures.

In addition, the illumination apparatus according to the presentembodiment may include a rectifier 200, a control signal generator 210,a switch unit 220, a current controller 230, a total current controller240, and a light emitting unit 250.

The rectifier 200 may rectify an AC voltage having positive and negativevalues and convert the AC voltage into a driving voltage Vin in the formof a rectifying current voltage. One of various known rectifiercircuits, such as a diode bridge circuit including diodes, may beadopted as the rectifier 200.

The control signal generator 210 may detect the driving voltage Vin andgenerate sampling signals COM0 to COM1, switch control signals SW1 toSW3, and current control signals SC1 to SC4 according to the magnitudeof the detected driving voltage Vin. The sampling signals COM0 to COM3may be applied to the total current controller 240, and the switchcontrol signals SW1 to SW3 may be applied to the switch unit 220. Also,the current control signals SC1 to SC4 may be respectively applied todriving current controllers 231 to 234 of the current controller 230.

The switch unit 220 may be provided between the driving voltage Vin andthe light emitting unit 250. Also, the switch unit 220 may include aplurality of switches, each of which may have a short circuit or beopened in response to the switch control signals SW1 to SW3.

The current controller 230 may include a plurality of driving currentcontrollers 231, 232, 233, and 234. The driving current controllers 231,232, 233, and 234 may be respectively connected to cathode terminals ofthe LEDs L21, L22, L23, and L24. The current control signals SC1 to SC4may be applied to the driving current controllers 231, 232, 233, and234. The driving current controllers 231, 232, 233, and 234 may beenabled or disabled in response to the applied current control signalsSC1 to SC4.

For example, when the current control signals SC1 to SC4 are enabled toa high level, the driving current controllers 231, 232, 233, and 234 mayhave predetermined current drivability and perform operations.Conversely, when the current control signals SC1 to SC4 are disabled toa low level, the driving current controllers 231, 232, 233, and 234 maybe put into a high-impedance state or floated state and may not performcurrent drive operations. Also, the target voltages Vt1 to Vt4 may beapplied to the driving current controllers 231, 232, 233, and 234. Whenthe driving current controllers 231, 232, 233, and 234 remain enabled,the target voltages Vt1 to Vt4 may determine the amount of current bywhich the illumination apparatus is driven.

The driving current controllers 231 to 234 constituting the currentcontroller 230 may be the same as described in the first embodiment.Thus, a description thereof will be omitted here.

Accordingly, when the current control signals SC1 to SC4 are enabled, abuffer may be enabled and receive the output of an amplifier. The outputof the amplifier may change a gate-source voltage Vgs of a transistorvia the buffer. The changed gate-source voltage Vgs may vary a drivingcurrent. The varied driving current may flow through a detectionresistor, and a voltage detected by the detection resistor may beapplied to a negative input terminal of the amplifier. The voltagedetected by the detection resistor may be characterized by following atarget voltage applied to a positive input terminal of the amplifier.

Therefore, as the target voltage increases, a driving current set byeach of the driving current controllers 231 to 234 may also increase.

The total current controller 240 may receive sampling signals COM0 toCOM3 of the control signal generator 210. The sampling signals COM0 toCOM3 may be input in the form of digital data. Accordingly, the totalcurrent controller 240 may perform DAC operations and generate targetvoltages Vt1 to Vt4. The target voltages Vt1 to Vt4 may be respectivelyinput to the driving current controllers 231, 232, 233, and 234. Thetarget voltages Vt1 to Vt4 may have the same value or different values.

The light emitting unit 250 may include a first LED L21, a second LEDL22, a third LED L23, and a fourth LED L24. Also, the light emittingunit 250 may be connected between the switch unit 220 and the currentcontroller 230. Cathode electrodes of the LEDs L21, L22, L23, and L24may be respectively connected to the driving current controllers 231,232, 233, and 234. Also, diodes D21, D22, and D23 may be connected amongthe LEDs L21, L22, L23, and L24. The diodes D21, D22, and D23 may have aforward connection relationship among the LEDs L21, L22, L23, and L24.For example, when the first LED L21 and the second LED L22 areelectrically connected in series, the diode D21 connected between thetwo LEDs L21 and L22 may supply current from the first LED L21 to thesecond LED L22 through a forward connection structure. Also, the diodesD21, D22, D23, and D24 may be connected in a reverse direction in acurrent path from the switch unit 220 toward the current controller 230.As a result, direct application of the driving voltage Vin through theswitch unit 220 to the current controller 230 may be prevented.

FIG. 8 is a circuit diagram of the control signal generator 210according to the second example embodiment of the present invention.

Referring to FIG. 8, the control signal generator 210 may include acomparison unit 211 and a logic combination unit 212.

The comparison unit 211 may include a plurality of comparators 2110 to2115. A reference voltage VF may be applied to a negative input terminalof each of the comparators 2110 to 2115, and a voltage obtained bydividing the driving voltage Vin by a resistor may be applied to apositive input terminal thereof. Thus, two resistors may be connected inseries to each path, and a voltage detected at a node between resistorsmay be input to the positive input terminal of each of the comparators2110 to 2115.

The comparators 2110 to 2115 may perform comparison operations andgenerate sampling signals COM0 to COM5.

For instance, when resistors R21 to R26 obey the relationshipR26>R25>R24>R23>R22>R21, and a resistor Rref connected to the drivingvoltage Vin has a predetermined resistance which is the same for eachpath, the output sampling signals COM0 to COM5 may be changed from(000000) to (111111) with a rise in the driving voltage Vin.

In addition, the comparison unit 211 according to the present embodimentmay be replaced by the comparison unit 112 according to the firstembodiment. The number of serial resistors of the comparison unit 112according to the first embodiment and the number of comparators may varyaccording to the number of output sampling signals.

The sampling signals COM0 to COM5 output by the comparison unit 211 maybe supplied to the total current controller 240 and supplied to thelogic combination unit 212.

The logic combination unit 212 may receive the sampling signals COM0 toCOM5 output by the comparison unit 211 and perform logic operations onthe sampling signals COM1 to COM5. As a result, the switch controlsignals SW1 to SW3 and the current control signals SC1 to SC4 may begenerated.

The logic combination unit 212 may include a combination of logicdevices that may be variously selected according to phases of the inputsampling signals COM0 to COM5 and phases of output switch controlsignals SW1 to SW3 or current control signals SC1 to SC4. For example,the logic combination unit 212 may include a programmable logic array orprogrammable array logic.

Also, the number of sampling signals may not be specifically limited butmay be variously selected according to the number of output switchcontrol signals and the number of current control signals.

FIG. 9 is a circuit diagram of the switch unit 220 according to thesecond example embodiment of the present invention.

Referring to FIG. 9, the switch unit 220 may include three switches 221,222, and 223, and each of the switch units 221, 222, and 223 may includeswitches QW1 to QW3 and control transistors QS1 to QS3.

Each of the switch transistors QW1 to QW3 and the control transistorsQS1 to QS3 may be a metal-oxide-semiconductor field effect transistor(MOSFET) and selectively have an n conductivity type or a p conductivitytype. When each of the switch transistors QW1 to QW3 is an n-MOSFET, adrain terminal of the n-MOSFET may be connected to the driving voltageVin, and resistors RZ1 to RZ3 may be connected between drain and gateterminals of the switch transistors QW1 to QW3. Also, zener diodes DZ1to DZ3 may be provided between gate and source terminals of the switchtransistors QW1 to QW3. When a surge voltage, which is a sudden highvoltage, is applied to gate terminals of the zener diodes DZ1 to DZ3,the zener diodes DZ1 to DZ3 may be clipped to a constant level. Also,the switch transistors QW1 to QW3 may perform switch operations usingthe resistors RZ1 to RZ3 connected between the gate and drain terminalsof the switch transistors QW1 to QW3 with the control transistors QS1 toQS3 cut off.

The control transistors QS1 to QS3 may be respectively connected betweengate terminals of the switch transistors QW1 to QW3 and ground, and theswitch control signals SW1 to SW3 may be applied to the gate terminalsof the control transistors QS1 to QS3.

When the switch control signals SW1 to SW3 are enabled to a high level,the control transistors QS1 to QS3 may be turned on. Thus, the gateterminals of the switch transistors QW1 to QW3 may be disabled to a lowlevel. Accordingly, the switch transistors QW1 to QW3 may be turned off.

When the switch control signals SW1 to SW3 are disabled to a low level,the control transistors QS1 to QS3 may be turned off. Also, a voltagehaving a predetermined level may be applied to the switch transistorsQW1 to QW3 due to resistors RZ1 to RZ3 connected between gate and drainterminals of the switch transistors QW1 to QW3. In particular, a currentpath including the driving voltage Vin and the resistors RZ1 to RZ3 maybe cut off due to the cut-off control transistors QS1 to QS3. Thus, avoltage having substantially the same level as the driving voltage Vinmay be applied to the gate terminals of the switch transistors QW1 toQW3. Accordingly, the switch transistors QW1 to QW3 of the switch unit220 may be turned on.

For brevity, when a level of a switch control signal appropriate forturning on a switch transistor is applied, the switch control signal maybe described as being enabled. Also, when a switch control signalappropriate for turning on the switch transistor is applied, the switchcontrol signal may be described as being disabled.

When the switches 221, 222, and 223 are turned on, the driving voltageVin may be applied to the LEDs L21, L22, L23, and L24 through the nodesN1, N2, and N3.

In addition, an operation of the illumination apparatus according to thepresent embodiment will be described with reference to Table 2.

TABLE 2 First Second Third Fourth driving driving driving drivingcurrent current current current First Second Third controller controllercontroller controller switch switch switch 231 232 233 234 221 222 223VF ≦ Vin < 2VF ON ON ON ON ON OFF OFF ON ON ON ON ON ON OFF 2VF ≦ Vin <3VF OFF ON OFF ON OFF ON OFF 3VF ≦ Vin OFF OFF OFF ON OFF OFF ON

Table 2 shows an example of the operation of the illumination apparatusof FIG. 7.

Initially, the switch control signal SW1 may be enabled, and theremaining switch control signals may be disabled. Thus, only the switchtransistor QW1 may be turned on, and the first switch 221 may go into aconduction state. The driving voltage Vin may be applied through theswitch transistor QW1 to the first node N1.

Also, the first through fourth driving current controller 231 through234 may be enabled in response to the applied current control signalsSC1 to SC4. In addition, the target voltages Vt1 to Vt4 may be appliedby the total current controller 240 to the first through fourth drivingcurrent controllers 231 to 234. The target voltages Vt1 to Vt4 may havethe same value.

Accordingly, a current path including the first node N1, the first LEDL21, and the first driving current controller 231 may be formed due tothe turned-on first switch 221, and the first LED L21 may perform alight emitting operation. Also, a current path including the first nodeN1, the second LED L22, and the second driving current controller 232may be formed, a current path including the first node N1, the third LEDL23, and the third driving current controller 233 may be formed, and acurrent path including the first node N1, the fourth LED L24, and thefourth driving current controller 234 may be formed. This means that therespective LEDs L21 to L24 are connected in parallel to one another andperform light emitting operations.

Furthermore, additional diodes may be provided between the respectivenodes and the LEDs L21 to L24 to cut off the flow of a backward currentbetween anode terminals and cathode terminals of the LEDs.

When the switch control signals SW1 and SW2 are enabled, the firstswitch 221 and the second switch 222 may be turned on. Thus, a drivingvoltage Vin may be applied to a first node N1 through the turned-onfirst switch 221, and the driving voltage Vin may be applied to a secondnode N2 through the turned-on second switch 222. Also, the enabledcurrent control signals SC1 to SC4 may be applied to the first throughfourth driving current controllers 231 to 234. Thus, the first throughfourth driving current controllers 231 to 234 may be enabled. Also,target voltages Vt1 to Vt4 may be respectively applied to the drivingcurrent controllers 231 to 234. The target voltages Vt1 to Vt4 may havethe same value.

Accordingly, a current path including the LED L21 and the first drivingcurrent controller 231 may be formed. The driving voltage Vin may beapplied from the first node N1 to the current path, and the drivingvoltage Vin may be applied from the second node N2 to the current path.Also, a current path including the LED L22 and the second drivingcurrent controller 232 may be formed. Furthermore, the LED L23 mayreceive the driving voltage Vin from the first node N1 and receive thedriving voltage Vin from the second node N2. Also, the LED L24 mayreceive the driving voltage Vin from the first node N1.

Accordingly, when the switch control signals SW1 and SW2 are enabled andthe respective driving current controllers 231 to 234 are enabled, therespective LEDs L21 to L24 may perform parallel light emittingoperations. This means that the LEDs L21 to L24 are not affected bylight emitting operations of other adjacent LEDs but independentlyperform light emitting operations at the same time.

Diodes D21 to D23 may be provided among the LEDs L21 to L24. The diodesD21 to D23 may be provided to cut off the flow of a backward currentwhen a reverse bias is applied between anode terminals and cathodeterminals of adjacent LEDs.

When the switch control signal SW2 is enabled, the second switch 222 maybe turned on. Thus, the driving voltage Vin may be applied to the secondnode N2.

Also, the current control signals SC2 and SC4 may be enabled. Thus, thesecond driving current controller 232 and the fourth driving currentcontroller 234 may be enabled. The target voltages Vt2 and Vt4 may beapplied to the enabled driving current controllers 232 and 234. Theapplied target voltages Vt2 and Vt4 may have the same value.

A current path including the second node N2, the LED L21, the diode D21,the LED L22, and the second driving current controller 232 may be formedin response to the switch control signal SW2 and the current controlsignals SC2 and SC4. Also, the driving voltage Vin of the second node N2may be applied to the current path, and the amount of current flowingthrough the current path may be determined by the target voltage Vt2applied to the second driving current controller 232.

A current path including the LED L23, the diode D23, the LED L24, andthe fourth driving current controller 234 may be formed parallel to theabove-described current path. The driving voltage Vin of the second nodeN2 may be applied to the current path, and the amount of current flowingthrough the current path may be determined by the target voltage Vt4applied to the fourth driving current controller 234.

The above-described operation may be enabled by a serial connectionstructure of two LEDs. Also, two serial connection structures may beprovided and connected in parallel to each other.

In addition, when the switch control signal SW3 is enabled, the thirdswitch 223 may be turned on. Thus, the driving voltage Vin may beapplied to the third node N3 through the turned-on third switch 223.

Furthermore, the current control signal SC3 may be enabled and theremaining current control signals disabled. Thus, only the fourthdriving current controller 234 may be enabled and perform a currentdrive operation. That is, a current path including the LED L21, thediode D21, the LED L22, the diode D22, the LED L23, the diode D23, theLED L24, and the fourth driving current controller 234 may be formed.The formed current path may include four LEDs connected in series.Current flowing through the current path may be determined by the targetvoltage Vt4 applied to the fourth driving current controller 234.

Due to the above-described operations, the LEDs can be directly anddiscretely driven by the driving current controller and connected invarious forms to enable light emitting operations.

In the present embodiment, a target voltage determined by the totalcurrent controller can be applied to the driving current controller. Thetarget voltage can determine the driving current of the driving currentcontroller.

As described in the first embodiment with reference to FIGS. 5 and 6,the total current amount of the illumination apparatus can be setconstant, and the currents flowing through respective current paths canbe set constant. Therefore, power consumption can be appropriatelydivided, and the luminance of each of the LEDs can be controlled to beconstant.

As explained thus far, in one embodiment of the present invention, anelectrical connection relationship among a plurality of LEDs can beappropriately changed with fluctuations in the magnitude of an ACvoltage for driving the plurality of LEDs so that all of the pluralityof LEDs employed in the illumination apparatus can emit light. Thus,longer light emission by only some of the LEDs employed in theillumination apparatus, which leads to earlier deterioration of thoseLEDs compared to other LEDs, can be prevented.

In addition, when necessary, the total current supplied to all the LEDscan be controlled to be constant or current supplied to each of the LEDscan be controlled to be constant.

Embodiment 3

Meanwhile, the illumination apparatus using the semiconductor lightemitting element according to the first example embodiment of thepresent invention described with reference to FIGS. 1 to 6 and theillumination apparatus using the semiconductor light emitting elementaccording to the second example embodiment of the present inventiondescribed with reference to FIGS. 7 and 9 may be configured to perform afree voltage function, if necessary, even though a separate additionalcircuit for performing the free voltage function is not added.

Hereinafter, although an implementation example of the free voltagefunction according to the present invention (i.e., the illuminationapparatus of the light emitting element according to the third exampleembodiment) will be described with reference to the illuminationapparatus using the semiconductor light emitting element according tothe first example embodiment of the present invention described withreference to FIGS. 1 to 6 for convenience of explanation andunderstanding, it should be noted that the same technical scope may beequally applied to other example embodiments of the present invention.

The same technical scope as the contents described above cites theabove-mentioned description about the first example embodiment and thesecond example embodiment, and hereinafter, a configuration forimplementing the free voltage function and a function thereof will bemainly described.

First, a key idea for implementing the free voltage function in thepresent invention is to detect a standard of the AC power to which theillumination apparatus of the light emitting element according to thethird example embodiment is connected (i.e., an effective voltage valueof the AC power input to the illumination apparatus of the lightemitting element according to the third example embodiment) and tocontrol a series and parallel connection relationship between a firstlight emitting group L31 to a fourth light emitting group L34 so as toensure that the first light emitting group L31 to the fourth lightemitting group L34 are smoothly driven under the detected standard ofthe AC power. For example, it is assumed that the light emitting unitconfigured to include the first light emitting group to the fourth lightemitting group, as an illumination apparatus (not shown) of a sequentialdriving type of light emitting element according to the related art isconfigured to have the first forward voltage level VF1 of 50V, thesecond forward voltage level VF2 of 100V, the third forward voltagelevel of 150V, and the fourth forward voltage level VF4 of 200V. In thiscase, when the illumination apparatus of the light emitting elementaccording the related art is connected to the AC power of 220V(rms) or277V(rms), the first light emitting group to the fourth light emittinggroup may be all operated in a state in which the first light emittinggroup to the fourth light emitting group are connected in series witheach other, but when the illumination apparatus of the light emittingelement according the related art is connected to the AC power of120V(rms), the first light emitting group to the fourth light emittinggroup may not be all operated in the state in which the first lightemitting group to the fourth light emitting group are connected inseries with each other. That is, according to the related art, in thecase in which the illumination apparatus of the light emitting elementis connected to the AC power of 120V(rms), there is a problem that thethird light emitting group and the fourth light emitting group of thefirst light emitting group to the fourth light emitting group connectedin series with each other are not continuously emitted. Similarly,according to the related art, in a state in which a first set of lightemitting groups (the first light emitting group and the second lightemitting group connected in series with each other) and a second set oflight emitting groups (the third light emitting group and the fourthlight emitting group connected in series with each other) are connectedin parallel to each other, when the illumination apparatus of the lightemitting element is connected to the AC power of 220V(rms) or 277V(rms),there is a problem that power efficiency is deteriorated.

In order to solve the problems as described above, the illuminationapparatus of the light emitting element according to the third exampleembodiment of the present invention may be configured to detect anaverage voltage level per period of the driving voltage Vin and comparethe detected average voltage level with a first average voltagereference level which is preset to determine a standard of the AC powerto which the illumination apparatus is currently connected (i.e., theeffective voltage level supplied by the connected AC power). Morespecifically, for example, the illumination apparatus of the lightemitting element according to the third example embodiment of thepresent invention may accumulate the driving voltage Vin supplied duringpredetermined periods (e.g., 10 to 40 periods) and detect the averagevoltage level per period of the driving voltage Vin based on theaccumulated driving voltage Vin.

That is, the AC power of 120V(rms) has the average voltage level perperiod of the driving voltage Vin of a specific value, the AC power of220V(rms) has the average voltage level per period of the drivingvoltage Vin of another specific value, and the AC power of 277V(rms) hasthe average voltage level per period of the driving voltage Vin of stillanother specific value. Therefore, by detecting the average voltagelevel per period of a supplied rectified voltage, the standard of the ACpower to which the illumination apparatus of the light emitting elementaccording to the third example embodiment is connected may bedetermined. Specific numeric values mentioned above are merelyillustrative, and various numeric values may be used, if necessary. Forexample, the AC power may also have effective voltages of 100V, 300V,and the like, and it will be apparent to those skilled in the art thatthe present invention may be applied to the above-mentioned all cases.In addition, although the example embodiment configured to determine thestandard (effective voltage) of the AC power to which the illuminationapparatus is currently connected, by detecting the average voltage levelper period of the driving voltage Vin has been described above, it willbe apparent to those skilled in the art that the above-mentionedprinciple may also be equally applied to the illumination apparatus ofthe light emitting element according to the third example embodimentconfigured to include a power factor compensator (not shown). That is,in the case in which the illumination apparatus of the light emittingelement according to the third example embodiment is configured toinclude the power factor compensator, the illumination apparatus of thelight emitting element according to the third example embodiment may beconfigured to determine performance of the AC power to which theillumination apparatus of the light emitting element according to thethird example embodiment is connected, by detecting the average voltagelevel per period of a power factor compensated driving voltage Vinsupplied to the light emitting unit 350. Hereinafter, for convenience ofexplanation and understanding, as shown in FIG. 10, the description willbe provided based on an example embodiment in which the illuminationapparatus of the light emitting element according to the third exampleembodiment does not include the power factor compensator and isconfigured to determine the standard of the AC power by detecting theaverage voltage level per period of the driving voltage Vin, but thepresent invention is not limited thereto.

Meanwhile, more preferably, according to an example embodiment, theillumination apparatus of the light emitting element according to thethird example embodiment may be configured so as not to determine anexact standard of the AC power to which the illumination apparatus ofthe light emitting element according to the third example embodiment isconnected, but to compare the average voltage level per period of thedriving voltage Vin with the first average voltage reference level whichis preset, and open and close the switch unit 120 depending on thecomparison result. Here, the first average voltage reference level maybe a value corresponding to a specific effective voltage of the AC powerfor controlling a series and parallel connection relationship of thefirst light emitting group L31 to the fourth light emitting group L34.That is, the illumination apparatus of the light emitting elementaccording to the third example embodiment may be configured to onlydetermine whether the effective voltage of the AC power to which theillumination apparatus of the light emitting element according to thethird example embodiment is connected is large enough to drive the firstlight emitting group L31 to the fourth light emitting group L34 in astate in which the first light emitting group L31 to the fourth lightemitting group L34 are connected in series with each other, or is smallenough to drive the first light emitting group L31 to the fourth lightemitting group L34 in a state in which the first light emitting groupL31 to the fourth light emitting group L34 are divided intopredetermined subsets so as to be connected in parallel to each other,and control the open and close of the switch unit 120 based on theabove-mentioned determination. For example, in the example describedabove (in the case in which the light emitting unit 350 is configured tohave the first forward voltage level VF1 of 50V, the second forwardvoltage level VF2 of 100V, the third forward voltage level VF3 of 150V,and the fourth forward voltage level VF4 of 200V), when the AC power towhich the illumination apparatus is connected has the effective voltageof 220V or 277V, the AC power has the effective voltage which is largeenough to drive the first light emitting group L31 to the fourth lightemitting group L34 which are connected in series with each other, and onthe other hand, when the AC power to which the illumination apparatus isconnected has the effective voltage of 120V, the AC power has theeffective voltage which is small enough to drive the first lightemitting group L31 to the fourth light emitting group L34 in the statein which the first light emitting group L31 to the fourth light emittinggroup L34 are divided into predetermined subsets so as to be connectedin parallel to each other. Therefore, according to an exampleembodiment, the illumination apparatus of the light emitting elementaccording to the third example embodiment of the present invention maydetermine performance of the AC power to which the illuminationapparatus is currently connected, by setting the first average voltagereference level so as to correspond to any reference effective voltagebetween 120V(rms) and 277V(rms) (e.g., 200V(rms)) and comparing theaverage voltage level per period of the driving voltage Vin with thefirst average voltage reference level which is preset. Of course,depending on the configuration of the example embodiment, two or moreaverage voltage reference levels may also be used to determine standardsof various AC powers. For example, the first average voltage referencelevel corresponding to 120V(rms), a second average voltage referencelevel corresponding to 220V(rms), and a third average voltage referencelevel corresponding to 277V(rms) may also be used.

In order to perform the function as described above, as shown in FIG.10, the illumination apparatus of the light emitting element accordingto the third example embodiment of the present invention may include therectifier 100, a control signal generator 310, the switch unit 120, acurrent controller 330, a total current controller 340, and the lightemitting unit 350.

Since the configuration and the function of the rectifier 100, theswitch unit 120, the current controller 330, the total currentcontroller 340, and the light emitting unit 350 among the components asdescribed above are substantially similar to the correspondingconfigurations of the first example embodiment and the second exampleembodiment described above, the overlapped descriptions are cited.Hereinafter, the present example embodiment will be described based ondifferences.

First, the light emitting unit 350 may be configured to include aplurality of light emitting groups, and the plurality of light emittinggroups included in the light emitting unit 350 may be configured tocontrol a series and parallel connection relationship therebetweenaccording to a control of the control signal generator 310 and to besequentially driven at the same time. Although FIG. 10 discloses thelight emitting unit 350 including four light emitting groups from thefirst light emitting group L31 to the fourth light emitting group L34,it will be apparent to those skilled in the art that the number of lightemitting groups included in the light emitting unit 350 may be variouslychanged, if necessary. However, hereinafter, the description will beprovided based on an example embodiment in which the light emitting unit350 includes the four light emitting groups for convenience ofexplanation and understanding, but the present invention is not limitedthereto. For example, the light emitting unit 350 may also include nlight emitting groups from the first light emitting group L31 to an n-th(n is a positive integer of two or more) light emitting group (notshown), and it will be apparent to those skilled in the art that thismodification falls in the scope of the present invention as long as itincludes the technical gist of the present invention.

Meanwhile, depending on the configuration of the example embodiment, thefirst light emitting group L31 to the fourth light emitting group L34may have the same forward voltage level as each other, or forwardvoltage levels different from each other. For example, in the case inwhich the first light emitting group L31 to the fourth light emittinggroup L34 are configured to include the different number of lightemitting elements or in the case in which the first light emitting groupL31 to the fourth light emitting group L34 have different types ofseries or parallel or series and parallel connection relationship, thefirst light emitting group L31 to the fourth light emitting group L34have forward voltage levels different from each other. However,hereinafter, for convenience of explanation and understanding, thepresent example embodiment will be described based on an exampleembodiment in which the light emitting unit 350 is configured to havethe first forward voltage level VF1 of 50V, the second forward voltagelevel VF2 of 100V, the third forward voltage level VF3 of 150V, and thefourth forward voltage level VF4 of 200V.

In order to implement the free voltage function as described above, thecontrol signal generator 310 according to the third example embodimentof the present invention is configured to detect the average voltagelevel per period of the driving voltage Vin and determine the standardof the AC power to which the illumination apparatus is currentlyconnected, based on the detected average voltage level. In addition, thecontrol signal generator 310 is configure to generate switch controlsignals SW1 to SW3 according to the determined standard of the AC powerto output the switch control signals SW1 to SW3 to the first switch 121to the third switch 123. For example, in the case in which the standardof the AC power connected to the illumination apparatus needs to connectthe first light emitting group L31 to the fourth light emitting groupL34 to be in parallel to each other, for example, in the case in whichthe AC power connected to the illumination apparatus is 60V(rms), thecontrol signal generator 310 is configured to generate the switchcontrol signals SW1 to SW3 that turn on all of the first switch 121 tothe third switch 123 to output the switch control signals SW1 to SW3 tothe first switch 121 to the third switch 123. Accordingly, all of thefirst switch 121 to the third switch 123 are tuned on, such that all ofthe first light emitting group L31 to the fourth light emitting groupL34 are connected in parallel to each other to be driven.

In addition, in the case in which the standard of the AC power connectedto the illumination apparatus needs to divide the first light emittinggroup L31 to the fourth light emitting group L34 into the subsets to beconnected in parallel to each other, for example, in the case in whichthe AC power connected to the illumination apparatus is 120V(rms), thecontrol signal generator 310 is configured to generate the switchcontrol signals SW1 to SW3 that turn off the first switch 121 and thethird switch 123 and turn on the second switch 122 to output the switchcontrol signals SW1 to SW3 to the first switch 121 to the third switch123. Accordingly, only the second switch 122 is turned on, such that afirst set of light emitting groups (the first light emitting group L31and the second light emitting group L32 connected in series with eachother) and a second set of light emitting groups (the third lightemitting group L33 and the fourth light emitting group L34 connected inseries with each other) are connected in parallel to each other to bedriven independently from each other. In addition, in this state, thefirst light emitting group L31 and the second light emitting group L32within the first set of light emitting groups (the first light emittinggroup L31 and the second light emitting group L32 connected in serieswith each other) are sequentially driven according to the voltage levelof the driving voltage Vin, and independently from those describedabove, the second light emitting group L32 and the third light emittinggroup L33 within the second set of light emitting groups (the thirdlight emitting group L33 and the fourth light emitting group L34connected in series with each other) are sequentially driven accordingto the voltage level of the driving voltage Vin.

In addition, in the case in which the standard of the AC power connectedto the illumination apparatus may drive the first light emitting groupL31 to the fourth light emitting group L34 to be in series with eachother, for example, in the case in which the AC power connected to theillumination apparatus is 220V(rms), the control signal generator 310 isconfigured to generate the switch control signals SW1 to SW3 that turnoff all of the first switch 121 to the third switch 123 to output theswitch control signals SW1 to SW3 to the first switch 121 to the thirdswitch 123. Accordingly, all of the first light emitting group L31 tothe fourth light emitting group L34 are connected in series with eachother to be sequentially driven according to the voltage level of thedriving voltage Vin.

Meanwhile, since the average voltage level per period of the drivingvoltage Vin is not varied over time and is constant, the above-mentionedseries and parallel connection control is performed only once when theillumination apparatus of the light emitting element according to thethird example embodiment is initially started.

In addition, according to an example embodiment, the control signalgenerator 310 and the current controller 330 according to the thirdexample embodiment of the present invention may be configured to performa series of functions for controlling a sequential driving of at leastsome of the first light emitting group L31 to the fourth light emittinggroup L34.

The above-mentioned sequential driving control of the first lightemitting group L31 to the fourth light emitting group L34 may beimplemented by the control signal generator 310 that detects aninstantaneous value of the driving voltage Vin and selectively activatesa first driving current controller 331 to a fourth driving currentcontroller 334 based on the detected instantaneous value. Morespecifically, the control signal generator 310 according to the presentinvention may control operation states of the first light emitting groupL31 to the fourth light emitting group L34 by controlling activation andinactivation of the first driving current controller 331 to the fourthdriving current controller 334, respectively, depending on a comparisonresult input from a comparing module 520.

The first driving current controller 331, the second driving currentcontroller 332, the third driving current controller 333, and the fourthdriving current controller 334 may be activated or inactivated accordingto the control of the control signal generator 310 as described above.More specifically, the first driving current controller 331 may beconfigured to connect or separate a first current path P1 thereto ortherefrom according to the control of the control signal generator 310,the second driving current controller 332 may be configured to connector separate a second current path P2 thereto or therefrom according tothe control of the control signal generator 310, and the third drivingcurrent controller 333 may be configured to connect or separate a thirdcurrent path P3 thereto or therefrom according to the control of thecontrol signal generator 310. Similarly, the fourth driving currentcontroller 334 may be configured to connect or separate a fourth currentpath P4 thereto or therefrom according to the control of the controlsignal generator 310.

In addition, similar to those described above about the first exampleembodiment and the second example embodiment, the first driving currentcontroller 331, the second driving current controller 332, the thirddriving current controller 333, and the fourth driving currentcontroller 334 may be configured to control a current value of a drivingcurrent IL of the light emitting element flowing through the respectiveswitches according to the control of the control signal generator 310.The first driving current controller 331 to the fourth driving currentcontroller 334 described above may be implemented to be identical orsimilar to the driving current controller according to the first exampleembodiment shown in FIG. 3.

In addition, according to an example embodiment, the control signalgenerator 310 according to the present invention may be furtherconfigured to control magnitude of the driving current IL of the lightemitting element according to the determined standard of the AC power.That is, for example, since input powers input to the illuminationapparatus of the light emitting element according to the third exampleembodiment from the AC power of 120V(rms), the AC power of 220V(rms),and the AC power of 277V(rms), respectively, need to be the same, thecontrol signal generator 310 according to the present invention isconfigured to control the magnitude of the driving current IL of thelight emitting element according to the determined standard of the ACpower so that deviation of the input power for each AC power may bewithin a range of 10% to 30%. That is, the control signal generator 310is configured to control a value of the driving current IL of the lightemitting element for each AC power so that a relationship which is ininverse proportion to the effective voltage value of the AC powerconnected to the illumination apparatus is established.

Meanwhile, FIG. 11A is a waveform diagram illustrating a relationshipbetween the driving voltage Vin and the driving current IL of the lightemitting element in the case in which the illumination apparatus of ahigh efficiency light emitting element according to the third exampleembodiment is connected to the AC power of 120V(rms), and FIG. 11B is awaveform diagram illustrating a relationship between the driving voltageVin and the driving current IL of the light emitting element in the casein which the illumination apparatus of the high efficiency lightemitting element according to the third example embodiment is connectedto the AC power of 220V(rms). In the case of the example embodimentsshown in FIGS. 11A and 11B, as described above, it is assumed that thelight emitting unit 350 is configured to have the first forward voltagelevel VF1 of 50V, the second forward voltage level VF2 of 100V, thethird forward voltage level VF3 of 150V, and the fourth forward voltagelevel VF4 of 200V. Hereinafter, operations of the cases in which theillumination apparatus of the light emitting element according to thethird example embodiment of the present invention as described above isconnected to the AC power of 120V(rms) and the AC power of 220 (rms),respectively, will be described with reference to FIGS. 11A and 11B.

First, as described above, the AC power of 120V(rms) is an AC powerwhich may not drive the first light emitting group L31 to the fourthlight emitting group L34 in the state in which the first light emittinggroup L31 to the fourth light emitting group L34 are connected in serieswith each other, and needs to be controlled to be divided into the firstset of light emitting groups (the first light emitting group L31 and thesecond light emitting group L32 connected in series with each other) andthe second set of light emitting groups (the third light emitting groupL33 and the fourth light emitting group L34 connected in series witheach other) so that the first set of light emitting groups and thesecond set of light emitting groups are connected in parallel to eachother. Therefore, the control signal generator 310 generates the switchcontrol signals SW1 to SW3 that turn off the first switch 121 and thethird switch 123 and turn on the second switch 122 to output the switchcontrol signals SW1 to SW3 to the first switch 121 to the third switch123, and accordingly, only the second switch 122 is turned on, such thatthe first set of light emitting groups (the first light emitting groupL31 and the second light emitting group L32 connected in series witheach other) and the second set of light emitting groups (the third lightemitting group L33 and the fourth light emitting group L34 connected inseries with each other) are connected in parallel to each other to bedriven independently from each other. In this state, a relationshipbetween the driving voltage Vin and the driving current IL of the lightemitting element flowing through the first set of light emitting groups,that is, the first light emitting group L31 and the second lightemitting group L32 connected in series with each other is shown in anupper side of FIG. 11A, and a relationship between the driving voltageVin and the driving current IL of the light emitting element flowingthrough the second set of light emitting groups, that is, the thirdlight emitting group L33 and the fourth light emitting group L34connected in series with each other is shown in a lower side of FIG.11A. As can be seen from the upper and lower sides of the FIG. 11A, thefirst set of light emitting groups and the second set of light emittinggroups are independently controlled in the state in which the first setof light emitting groups and the second set of light emitting groups areconnected in parallel to each other. Particularly, it may be seen thatthe first light emitting group L31 and the second light emitting groupL32 belonging to the first set of light emitting groups are sequentiallydriven according to the voltage level of the driving voltage Vin. Thatis, as shown in the upper side of the FIG. 11A, in a section in whichthe voltage level of the driving voltage Vin is the first forwardvoltage level VF1 or more and is less than the second forward voltagelevel VF2, the first driving current controller 331 is activated and thesecond driving current controller 332 is inactivated, such that only thefirst light emitting group L31 of the first set of light emitting groupsemits light. In addition, in a section in which the voltage level of thedriving voltage Vin is the second forward voltage level VF2 or more, thefirst driving current controller 331 is inactivated and the seconddriving current controller 332 is activated, such that all of the firstlight emitting group L31 and the second light emitting group L32 of thefirst set of light emitting groups are emitted. Therefore, it may beseen that the sequential driving according to the voltage level of thedriving voltage Vin is performed within the first set of light emittinggroups.

In addition, independently, the third light emitting group L33 and thefourth light emitting group L34 belonging to the second set of lightemitting groups are sequentially driven according to the voltage levelof the driving voltage Vin. That is, as shown in the lower side of theFIG. 11A, in a section in which the voltage level of the driving voltageVin is ‘the third forward voltage level VF3−the second forward voltagelevel VF2’ (VF3−VF2) or more and is less than ‘the fourth forwardvoltage level VF4−the second forward voltage level VF2’ (VF4−VF2), thethird driving current controller 333 is activated and the fourth drivingcurrent controller 334 is inactivated, such that only the third lightemitting group L33 of the second set of light emitting groups emitslight. In addition, in a section in which the voltage level of thedriving voltage Vin is ‘the fourth forward voltage level VF4−the secondforward voltage level VF2’ (VF4−VF2) or more, the third driving currentcontroller 333 is inactivated and the fourth driving current controller334 is activated, such that all of the third light emitting group L33and the fourth light emitting group L34 of the second set of lightemitting groups are emitted. Therefore, it may be seen that thesequential driving according to the voltage level of the driving voltageVin is performed within the second set of light emitting groups.

On the other hand, as described above, the AC power of 220V(rms) is anAC power that may drive the first light emitting group L31 to the fourthlight emitting group L34 in the state in which the first light emittinggroup L31 to the fourth light emitting group L34 are connected in serieswith each other. Therefore, all of the first switch 121 to the thirdswitch 123 are maintained in an opened state according to the control ofthe control signal generator 310, and the first light emitting group L31to the fourth light emitting group L34 are sequentially driven by thecontrol signal generator 310 in the state in which the first lightemitting group L31 to the fourth light emitting group L34 are connectedin series with each other. The above-mentioned process is shown in FIG.11B. That is, as shown in FIG. 11B, in the section in which the voltagelevel of the driving voltage Vin is the first forward voltage level VF1or more and is less than the second forward voltage level VF2, only thefirst driving current controller 331 is activated and other drivingcurrent controllers are inactivated, such that only the first lightemitting group L31 emits light. In addition, in the section in which thevoltage level of the driving voltage Vin is the second forward voltagelevel VF2 or more and is less than the third forward voltage level VF3,only the second driving current controller 332 is activated and otherdriving current controllers are inactivated, such that the first lightemitting group L31 and the second light emitting group L32 are emitted.In addition, in a section in which the voltage level of the drivingvoltage Vin is the third forward voltage level VF3 or more and is lessthan the fourth forward voltage level VF4, only the third drivingcurrent controller 333 is activated and other driving currentcontrollers are inactivated, such that the first light emitting groupL31 to the third light emitting group L33 are emitted. Finally, in asection in which the voltage level of the driving voltage Vin is thefourth forward voltage level VF4 or more, only the fourth drivingcurrent controller 334 is activated and other driving currentcontrollers are inactivated, such that the first light emitting groupL31 to the fourth light emitting group L34 are emitted. Therefore, ascan be seen from the above, in the case in which the illuminationapparatus is connected to the AC power of 220V(rms), it may be seen thatthe first light emitting group L31 to the fourth light emitting groupL34 are connected in series with each other to be sequentially drivenaccording to the voltage level of the driving voltage Vin.

In addition, as described above, the illumination apparatus of the lightemitting element according to the third example embodiment of thepresent invention may control the magnitude of the driving current IL ofthe light emitting element for each AC power so that power deviation foreach AC power of input power input to the illumination apparatus may bemaintained within 10% to 30%. For example, a driving current IL′ of thelight emitting element of the illumination apparatus of the lightemitting element according to the third example embodiment connected tothe AC power of 220V(rms) may be constant current-controlled to about ½of the driving current IL of the light emitting element of theillumination apparatus of the light emitting element according to thethird example embodiment connected to the AC power of 120V(rms). FIG.11A shows a driving current IL1 of a first light emitting element, adriving current IL2 of a second light emitting element, a drivingcurrent IL3 of a third light emitting element, and a driving current IL4of a fourth light emitting element of the illumination apparatus of thelight emitting element according to the third example embodimentconnected to the AC power of 120V(rms), and FIG. 11B shows a drivingcurrent IL1′ of the first light emitting element, a driving current IL2′of the second light emitting element, a driving current IL3′ of thethird light emitting element, and a driving current IL4′ of the fourthlight emitting element of the illumination apparatus of the lightemitting element according to the third example embodiment connected tothe AC power of 220V(rms). Referring to FIGS. 11A and 11B, it may beseen that magnitude of the driving current IL1′ of the first lightemitting element, magnitude of the driving current IL2′ of the secondlight emitting element, magnitude of the driving current IL3′ of thethird light emitting element, and magnitude of the driving current IL4′of the fourth light emitting element are constant current-controlled toabout ½ of magnitude of the driving current IL1 of the first lightemitting element, magnitude of the driving current IL2 of the secondlight emitting element, magnitude of the driving current IL3 of thethird light emitting element, and magnitude of the driving current IL4of the fourth light emitting element.

Hereinabove, various example embodiments of the illumination apparatusof the high efficiency light emitting element according to the presentinvention have been described with reference to the accompanyingdrawings. As described above, the illumination apparatus of the highefficiency light emitting element according to the present invention maycontrol the series and parallel connection relationship between thelight emitting groups according to the voltage level of the drivingvoltage, and may improve power efficiency thereof by controlling thesequential driving the light emitting groups, at the same time. Inaddition, the illumination apparatus of the high efficiency lightemitting element according to the present invention may further improvepower efficiency thereof by blocking an input of the rectified voltagein the compensation section.

What is claimed is:
 1. An illumination apparatus, comprising: arectifier configured to be connected to an alternating current (AC)power source and to perform a full-wave rectification for an applied ACvoltage, and to provide a rectified voltage which is full-wave rectifiedto a light emitting unit as a driving voltage, the light emitting unitcomprising a first light emitting group to an n-th light emitting group,n being a positive integer of at least two, and configured to emit lightby receiving the driving voltage from the rectifier; a control signalgenerator configured to generate a switch control signal for controllinga series and parallel connection relationship between the first lightemitting group to the n-th light emitting group according to an averagevoltage level per period of the driving voltage, and generate a currentcontrol signal for controlling a sequential driving of at least aportion of the first light emitting group to the n-th light emittinggroup according to the voltage level of the driving voltage; a switchunit configured to perform an on or off operation according to theswitch control signal, to selectively transfer the driving voltage; anda current controller comprising a first driving current controller to ann-th driving current controller connected to the first light emittinggroup to the n-th light emitting group, respectively, the first drivingcurrent controller to the n-th driving current controller configured tobe selectively activated according to the current control signal.
 2. Theillumination apparatus of claim 1, wherein the control signal generatoris configured to control the magnitude of a driving current of the lightemitting element according to the average voltage level per period ofthe driving voltage.
 3. A driving circuit of a light emitting elementconfigured to control driving of a light emitting unit comprising afirst light emitting group to an n-th light emitting group, n being apositive integer of two or more, the driving circuit comprising: arectifier configured to be connected to an alternating current (AC)power source, perform a full-wave rectification for an applied ACvoltage, and to provide a rectified voltage which is full-wave rectifiedto a light emitting unit as a driving voltage; a control signalgenerator configured to generate a switch control signal for controllinga series and parallel connection relationship between the first lightemitting group to the n-th light emitting group according to an averagevoltage level per period of the driving voltage, and generate a currentcontrol signal for controlling a sequential driving of at least aportion of the first light emitting group to the n-th light emittinggroup according to the voltage level of the driving voltage; a switchunit configured to perform an on or off operation according to theswitch control signal, to selectively transfer the driving voltage; anda current controller comprising a first driving current controller to ann-th driving current controller connected to the first light emittinggroup to the n-th light emitting group, respectively, the first drivingcurrent controller to the n-th driving current controller configured tobe selectively activated according to the current control signal.
 4. Thedriving circuit of claim 3, wherein the control signal generator isconfigured to control the magnitude of a driving current of the lightemitting element according to the average voltage level per period ofthe driving voltage.